Near ablation threshold nanomilling using femtosecond laser pulses

Metal nanomilling on copper thin film surfaces using single-shot near-infrared femtosecond laser pulses was demonstrated and characterized in this thesis. The measurements of ablated copper ions by a time-of-flight (TOF) technique and the measurements of the optical emission of excited copper atoms by a photomultiplier tube (PMT) provided an online diagnostic technique to monitor the nanomilling process. Two distinct ablation regimes were observed from these measurements as a function of peak incident fluence. The results from TOF technique showed that the kinetic energies of the ablated copper ions ranged from several hundred eV to a few KeV. The measurements of surface profile showed that there were two ablation regimes on the ablated copper surface at a peak incident fluence above 0.6 J/cm2. At incident fluence less than 0.6 J/cm2, only the nanomilled depth remains. And the highest precision of 2.5 nm can be achieved using single-shot nanomilling.